Mmmm....I'd question the use of the term 'vicious' - in the right hands such a curb could be used with great delicacy and precision - far more so than the supposedly (but far from it) innocuous snaffle in the wrong hands (which it usually is). Potentially severe - yes. But at least the port leaves room for the tongue, which many supposedly less severe bits don't do. Bear in mind also that incorrect use of a potentially severe bit can quickly render a horse unmanageable, so how likely is it that the bit was used in a severe manner? Without seeing the riders who used it, we really don't know.